Wheel

ABSTRACT

A wheel ( 10 ) comprises a main body ( 12 ) and is provided with at least one reinforcing structure ( 14 ) which increases the strength of the wheel ( 10 ). The reinforcing structure ( 14 ) is at least partially integrated inside the main body ( 12 ).

CROSS REFERENCE TO RELATED APPLICATION

This application is a national stage of PCT/EP2003/011485 filed Oct. 16,2003 and based upon DE 102 53 299.0 filed Nov. 15, 2002 under theInternational Convention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a wheel, having a main body and at least onereinforcing structure which increases the strength of the wheel.

2. Related Art of the Invention

Wheels of the aforementioned type are known in the art. DE 199 12 715A1, for example, discloses an aluminum compressor wheel, having areinforcing ring affording greater specific strength than aluminumarranged at the nave thereof. The reinforcing ring may be made from ahigh-strength plastic material, such as a thermoplastic materialreinforced with continuous fibers. This reduces the stresses occurringin the aluminum in the nave area.

SUMMARY OF THE INVENTION

The object of the invention is to propose a wheel of the generic typewhich is characterized by increased strength and which at the same timeis relatively easy to manufacture from a production engineeringstandpoint.

The distinguishing feature of the wheel according to the invention isthat the reinforcing structure is at least partially integrated insidethe main body. This makes it possible to increase the strength of thewheel in such a way that it is matched to the prevailing wheel stressesor those to be anticipated in operation. The strength can therefore beincreased particularly in the intensively stressed areas of the wheel,so that the main body has favorable operating characteristicsparticularly in these areas. At the same time, integration of a suitablereinforcing structure in the main body of the wheel is relatively easyto achieve from a production engineering standpoint. For example, thereinforcing structure can be at least partially integrally cast with themain body. The lost-wax casting process (precision casting process), forexample, in which a suitable reinforcing structure is integrated in awax model of the wheel and the wheel wax model is melted out during theactual wheel casting process, leaving the position of the reinforcingstructure especially well defined in the wheel material, is particularlysuited to this. Such a wheel manufacturing method permits a flexiblearrangement of the reinforcing structure in the main body, allowingdifferent reinforcing structures to be used, as required.

The main body advantageously has a nave component and a blade component,the reinforcing structure being arranged in the nave component and/or inthe blade component. This makes it possible to increase the overallstrength of the wheel, whilst at the same time being able to use thereinforcing structure, as necessary, to reinforce strength-criticalareas of the wheel.

According to one possible embodiment the reinforcing structure may takethe form of a prefabricated reinforcing element. For example, thereinforcing element may be a strengthening tube, which is integrated inthe nave component of the wheel. From a production engineeringstandpoint such a reinforcing element can be integrated with relativeease into a main body of the wheel to be cast. At the same time,reinforcing elements of differing geometry and/or strength can, wherenecessary, be provided in one and the same wheel, depending on thesphere of application of the wheel. In the case of a strengthening tubeits internal tube surface may form the whole or part of the nave holesurface. The reinforcing element may furthermore be manufactured fromthe same basic material as the wheel or from a different type of basicmaterial, the reinforcing structure being at least partially integratedin the basic material.

The reinforcing structure preferably has a mesh inlay. In this case themesh inlay may have a constant mesh width and/or one adapted to theparticular wheel geometry. It is furthermore possible for the mesh inlayto comprise a plurality of mesh components extending in a radialdirection and/or in an axial direction and/or in a peripheral directionrelative to the wheel. The different mesh components allow athree-dimensional stress condition occurring in the wheel to becompensated for in such a way that undesirable wheel deformations and/ordamage are avoided. The mesh inlay may also take the form of skeletallines extending helically from the inside outwards.

The mesh inlay may be arranged, at least in part, immediately below thesurface of the main body and/or at least partially at the surface of themain body. This allows the strength to be tailored to suit the stress onthe exposed surface of the main body. It is also possible, by means ofthe mesh inlay components situated at the exposed surface of the mainbody, to optimize the wear characteristics of the wheel. At least a partof the exposed surface of the wheel can also, if necessary, be coatedwith a high-strength reinforcing structure material. It is furthermorepossible, by means of a reinforcing structure in the form of a mesh, forexample, extending on the flow surfaces of the wheel, purposely topromote turbulence of the operating medium, thereby possibly improvingthe thermodynamic efficiency of the wheel.

According to one possible design variant the reinforcing structure mayadditionally have a reinforcing component arranged entirely externallyin relation to the main body and fixed thereto. This creates furtherpossibilities for flexibly increasing the strength of the wheel. At thesame time the reinforcing component can, if necessary, also be providedwith a reinforcing structure.

As a stiffening element at least partially reproducing the bladegeometry, the external reinforcing component is advantageously providedwith an inlay structure. Here too, the inlay structure is at leastpartially integrated in the stiffening element. Such stiffening elementsare relatively easy to cast. Furthermore, the main body of the wheel andthe stiffening element can, if necessary, be manufactured from differentmaterials.

According to an alternative embodiment the external reinforcingcomponent may take the form of a high-strength circular banding unit.This also permits flexible adjustment of the wheel strength to thestresses to be anticipated in operation of the wheel.

The reinforcing structure is preferably prestressed under a pretensilestress serving to increase the compressive strength. The desiredpretensile stressing of the reinforcing structure may be achievedthrough the use, during the casting process of a coefficient of thermalexpansion different from that of the material in the main body of thewheel. It is furthermore possible to build up corresponding pretensilestresses even before the actual casting process by means of an externalpretensile force in the reinforcing structure of the wheel.

Alternatively or in addition to this the reinforcing structure may havea multiplicity of reinforcing fibers freely distributed in the mainbody. Such reinforcing fibers are therefore not connected to one anotherand may be uniformly distributed or may be arranged in varyingconcentrations in different areas of the main body of the wheel. Theyare preferably made from a high-strength material.

The reinforcing structure advantageously contains high-strength metalfibers and/or carbon fibers and/or glass fibers. Such fibers areparticularly suitable as reinforcing material in order to obtainincreases in the strength of the wheel that can be flexibly adapted toanticipated wheel stresses.

The main body is preferably made using aluminum as basic material.Aluminum is a proven material for the manufacture of wheels and arelatively inexpensive compared to high-strength titanium.

The wheel may be a compressor wheel and in particular a compressor wheelfor an exhaust-gas turbocharger compressor wheel. The ever-increasingengine outputs of motor vehicles mean that correspondingly high strengthdemands are placed on such wheels, especially in the area of the nave,which demands can now be met by relatively inexpensive means.

Further advantages of the invention are set forth in the description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained on the basis of several preferredexemplary embodiments and with reference to a schematic drawing, inwhich:

FIG. 1 shows a schematic sectional representation of a part of a wheelaccording to the invention;

FIG. 2 shows a schematic top view of a part of the blade area of thewheel in FIG. 1;

FIG. 3 shows a schematic side view of a part of the wheel in FIG. 2;

FIG. 4 shows a schematic sectional representation of a part of a wheelaccording to the invention in an alternative embodiment and

FIG. 5 shows a schematic sectional representation of a reinforcingelement for a wheel according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 3 show different schematic views of part of a wheel 10 in afirst embodiment. The wheel 10 is a so-called “splitter blade”. Thewheel 10 comprises a main body 12, which has a nave component 16 and ablade component 18. Both the nave component 16 and the blade component18 are provided with a reinforcing structure 14. The mesh inlay 24 hasdiffering mesh structures and mesh widths in the nave component 16 andthe blade component 18. Mesh structures adapted to the respective stressloading are also provided in different areas of the nave component 16and the blade component 18. The mesh inlay 24 in both the nave component16 and the blade component 18 comprises mesh components 26, which extendin a radial direction, mesh components 28, which extend in an axialdirection, and mesh components 30 which extend in a peripheraldirection. Here the mesh inlay 24 extends over the entire main body 12of the wheel 10 to the exposed surface 31 thereof.

The wheel 10 in FIG. 1 is represented with a wheel blade which is turnedin a meridional plane. The mesh inlay 24 in the blade component 18 isarranged in a defined skeletal plane inside the blade represented andfulfils the function of supporting structure for the basic material. Inthe exemplary embodiment shown the mesh components and skeletalfilaments oriented axially, radially and peripherally both in the navecomponent 16 and in the blade component 18 are linked to one another atnodal points. The entire wheel 10 may be cast, for example, using aconventional aluminum alloy as main body material (basic material).According to FIG. 3 the blades of the wheel 10 are curved backwards. Toillustrate the wheel geometry the axis of rotation 40, the nave hole 42,the splitter blade inlet 46 and the wheel outlet 48 (see FIGS. 1 and 2in particular) are also represented in FIGS. 1 to 3.

FIG. 4 shows a wheel 10, which is of a design similar to that in FIGS. 1to 3. In contrast to the exemplary embodiment in FIGS. 1 to 3, the wheel10 in FIG. 4 is additionally provided with an external reinforcingcomponent 32, which takes the form of a stiffening element 34reproducing the blade geometry of the wheel 10. The reinforcingcomponent 32 is firmly connected to main body 12 of the wheel 10externally on the blade component 18. At the same time the stiffeningelement 34 is provided with an inlay structure 36, which likewise takesthe form of a mesh inlay extending in three dimensions. The reinforcingcomponent 32 designed as cover ring is connected to the respectiveblades of the wheel 10, for example as an integral casting. According toan alternative embodiment the external reinforcing component 32 may alsotake the form, where necessary, of a high-strength circular bandingunit. The remaining structure of the wheel 10 in FIG. 4 corresponds tothat in FIGS. 1 to 3.

FIG. 5 shows a schematic representation of a reinforcing element 20which can be integrated into a wheel and which takes the form of astrengthening tube 22. The reinforcing element 20 is intended forembedding in the nave component 16 of a wheel, its inside wall 44 atleast partially forming the wall of a nave hole of the wheel (forexample the nave hole 42 of the wheel 10). The strengthening tube 22 isprovided with reinforcing fibers 38 inlaid in the basic material. Thereinforcing fibers 38 are here not connected together but lieirregularly distributed in the basic material of the strengthening tube.The reinforcing element 20 can be prefabricated, for example, as aso-called “preform”, to be then laid in a mold for manufacturing of thewheel. In the case of a wheel having a strengthening tube 22, thestrengthening tube axis 22 corresponds to the axis of rotation 40 of thewheel. A wheel 10 of such a design may, where necessary, be additionallyor alternatively provided with at least one reinforcing element 20.

The aforementioned design features are especially suited to themanufacture of a compressor wheel and in particular of a compressorwheel for an exhaust-gas turbocharger for a motor vehicle. Aluminum, forexample, is suitable as basic material for the main body 12, whilst thereinforcing structure 14, may be composed of high-strength metal fibersor carbon fibers or glass fibers. The use of a reinforcing structure 14at least partially integrated inside the main body 12, particularly in acompressor wheel for an exhaust-gas turbocharger, means that possiblenave fractures can be prevented or at least decisively reduced evenunder extremely high wheel stresses. The facility for a widely varyingdesign of the reinforcing structure 14 now makes it possible andrelatively inexpensive to significantly increase the strength of thewheel 10, particularly in a radial direction. There is therefore no needto resort to relatively expensive materials such as titanium in order toobtain an adequately serviceable wheel. In production engineering termsthe reinforcing structure 14 in the form of a mesh inlay 24, acting ashigh-strength supporting skeleton, can be readily anchored in the wheelin the casting processing, making it possible to purposely reinforce theload-bearing capacity of the wheel in those areas in which the highestoperating stresses are usually to be expected. The operating stresses ofthe wheel 10 are absorbed by the reinforcing structure 14 owing to itsrelatively high strength in conjunction with the basic material (forexample aluminum) of the wheel 10. Here, stresses, in particular tensilestresses acting on the wheel 10 can be beneficially compensated for. Byarranging the mesh inlay 24 in an area of the wheel 10 close to thesurface, the reinforcing structure 14 is able, like a net, to catchoperating centrifugal stresses occurring in the wheel 10 like a net,forming tensile stresses. It is even possible, where necessary, tosubject the reinforcing structure 14 in the main body 12 to pretensilestresses on a principle similar to “prestressed concrete”, so that inthe event of compressive stresses acting of the main body 12 these canbe at least partially compensated for by the pretensile stresses. Owingto the prestressed reinforcing structure 14, therefore, a size-reducingtensile stress condition occurs in the main body 12 only in excess of aspecific operating speed of the wheel 10.

The differences in material characteristics, particularly in thestrength of the main body material and the reinforcing structurematerial, can give the wheel and in particular the blade componentdesirable damping characteristics. As a result, resonance stressesoccurring in wheel operation can be sustained without damage.

The high-strength material characteristics of the reinforcing structureand in particular the relatively high modulus of elasticity of thereinforcing structure material allow the thermal expansion of the wheelduring operation to be purposely reduced or limited, so that evenallowing for the centrifugal forces occurring during operation of thewheel a relatively tight wheel-fitting gap dimension can be preciselyadhered to. This is particularly important in compressor wheels forexhaust-gas turbochargers, which can reach operating temperatures of upto 250° C. A precisely maintainable gap dimension of a fitted wheelleads to a reduction of the ensuing friction losses and hence to anincrease in the efficiency of the overall system.

The reinforcing structure 14 composed of a fiber system is thereforearranged in the main body 12 of the wheel 10 in such a way that adefinite increase in strength, especially in a radial direction, islargely obtained in the critical wheel areas. This makes it possible toreduce any risk of fracture, especially in the nave component 16 due tothe high centrifugal forces and/or the thermal expansion duringoperation of the wheel 10. At the same time the wheel 10 with integrallycast reinforcing structure 14 can be manufactured relatively easily andinexpensively.

1. A wheel (10), comprising: a main body (12), and at least onereinforcing structure (14) for increasing a strength of the wheel (10),wherein the reinforcing structure (14) is at least partially integrallycast in the main body (12), and wherein the reinforcing structure (14)is prestressed under a pretensile stress serving to increase acompressive strength.
 2. The wheel as claimed in claim 1, wherein themain body (12) has a nave component (16) and a blade component (18), thereinforcing structure (14) being arranged in the nave component (16)and/or in the blade component (18).
 3. The wheel as claimed in claim 1,wherein the reinforcing structure (14) takes the form of a prefabricatedreinforcing element (20).
 4. The wheel as claimed in claim 3, whereinthe reinforcing element (20) takes the form of a strengthening tube(22), which is integrated in the nave component (16) of the wheel (10).5. The wheel as claimed in claim 1, wherein the reinforcing structure(14) has a multiplicity of reinforcing fibers (38) freely distributed inthe main body (12).
 6. The wheel as claimed in claim 1, wherein thereinforcing structure (14) has high-strength metal fibers and/or carbonfibers and/or glass fibers.
 7. The wheel as claimed in claim 1, whereinthe main body (12) is manufactured using aluminum as basic material. 8.The wheel as claimed in claim 1, wherein the wheel is a compressor wheeland in particular a compressor wheel for an exhaust-gas turbocharger ofa motor vehicle.
 9. A wheel (10), comprising: a main body (12), and atleast one reinforcing structure (14) for increasing a strength of thewheel (10), wherein the reinforcing structure (14) is at least partiallyintegrated inside the main body (12), wherein the reinforcing structure(14) is prestressed under a pretensile stress serving to increase acompressive strength, and wherein the reinforcing structure (14) has amesh inlay (24).
 10. The wheel as claimed in claim 9, wherein the meshinlay (24) comprises a plurality of mesh components (26, 28, 30)extending in a radial direction and/or in an axial direction and/or in aperipheral direction in relation to the wheel (10).
 11. The wheel asclaimed in claim 9, wherein the mesh inlay (24) is arranged, at least inpart, immediately below the surface (31) of the main body (12).
 12. Thewheel as claimed in claim 9, wherein the mesh inlay (24) is arranged atleast partially at the surface (31) of the main body (12).
 13. A wheel(10), comprising: a main body (12), and at least one reinforcingstructure (14) for increasing a strength of the wheel (10), wherein thereinforcing structure (14) is at least partially integrated inside themain body (12), wherein the reinforcing structure (14) is prestressedunder a pretensile stress serving to increase a compressive strength,and wherein the reinforcing structure (14) additionally has areinforcing component (32) arranged entirely externally in relation tothe main body (12) and fixed thereto.
 14. The wheel as claimed in claim13, wherein the external reinforcing component (32), as a stiffeningelement (34) at least partially reproducing the blade geometry, isprovided with an at least partially integrated inlay structure (36). 15.The wheel as claimed in claim 13, wherein the external reinforcingcomponent (32) takes the form of a high-strength circular banding unit.